1. Field of the Invention
The invention relates to medical devices and, in particular, to a device for positioning and stabilizing diagnostic or therapeutic devices used in medical procedures.
2. Background Information
In clinical practice, there are many different procedures utilized for various diagnostic, therapeutic, monitoring, or guidance applications. These are typically conducted by a highly skilled operator who relies heavily on the ability to simultaneously perform multiple tasks, such as viewing a monitor while positioning a probe or dissecting tissue while exerting separation force upon the walls of an incision. Examples of such medical tasks include, but are not limited to, invasive radiology (for breast biopsy), local anesthesia (for peripheral nerve blocks), invasive cardiology (for stent placement and deployment), vascular surgery (for measuring intravascular blood flow), and general surgery (for retraction of the incision walls or holding a hemostat clamping device).
By way of example, peripheral nerve blocks are used by anesthesiologists and pain doctors to anesthetize nerves that are involved in the transmission of pain signals during surgery or states of chronic disease. The image-acquisition procedure requires at least one of the operator's hands to be continually occupied at a high level of concentration and dexterity for probe manipulation. In general, the practitioner must carefully orient the probe and maintain it in relative contact with the anatomical region to acquire a good image. A second skilled operator must be employed to insert the needle, then deliver the required drug; undoubtedly a task requiring two hands.
Peripheral nerve blocks fall under the category of regional anesthesia, which indicates only a portion of the body is anesthetized and/or desensitized. This is in contrast to general anesthesia, in which the patient is placed into a state of complete unconsciousness. Nerve blocks entail the deposition of local anesthetics, such as lidocaine, which block the transmission of the pain signals for a variable amount of time. The major challenge for the clinician performing nerve blocks is related to finding the nerve of interest. Traditional anesthesiology approaches rely on palpating external landmarks on the skin, assuming that the anatomy below is normal, and subsequently inserting a needle attached to a nerve stimulator. When the needle contacts the nerve, a twitch occurs in the muscle that is interconnected with the nerve. By this method, the practitioner knows where to inject.
Because anatomy is variable, this technique results in significant failure rates, multiple needle passes, and significant potential for pain and injury to the nerve and adjacent structures. Modern ultrasound technologies allow the operator to guide his or her needle under live visualization to the structures of interest. The operator can then avoid multiple needle sticks, avoid structures (such as blood vessels), and confirm that the local anesthetic is spreading around the nerve of interest. However, current ultrasound approaches to performing nerve blocks and any other procedures (placement of intravenous catheters, breast biopsies, etc.) require that the operator hold the ultrasound probe in at least one hand in engagement with the anatomical region of interest. Once a satisfactory image of the structure is acquired, subtle movements of the hand holding the probe may result in degradation of the image, requiring a repositioning of the probe.
In addition to anatomical differences between patients, traditional landmark and nerve stimulator techniques can produce incomplete blockage of pain for patients because the drugs administered may not completely perfuse the nerves. Ultrasound not only enables the practitioner to visualize the target nerves and needle, but also the drugs deployed. If necessary he/she can reposition the needle and deploy drugs to the unblocked portions, ensuring a complete blockage of pain.
The pressure applied to the region of interest/treatment by the procedure guiding probe is critical. Too much pressure tends to distort the underlying tissues, making for an inaccurate image and pinching of internal tissues that may lead to misdirection of the needle. Too little pressure yields a bad image. During the procedure, the guiding probe is employed previous to needle insertion. Hence, the practitioner generally uses the “strong” hand (e.g. the right hand for a right-handed person) to guide and position the probe. This leaves the task of needle insertion either to the practitioner's weak hand or a second practitioner. The single-practitioner approach is rarely used in practice, both due to quality and safety concerns and also to prevailing medical practice rules and custom. Hence, two practitioners are, in fact, employed to perform the procedure (e.g. block, placement of intravenous catheters, breast biopsies). The second practitioner is needed to hold the probe, as the primary operator administers therapy—a task encompassing the injection of medicine, placement of the catheter, or performing the biopsy.
A solution to the problem of “too few hands” is taught in copending U.S. patent application Ser. No. 11/338,270, entitled BIOMEDICAL POSITIONING AND STABILIZATION SYSTEM by Katherine M. Hickey, et al., the teachings of which are expressly incorporated herein by reference. This teaching provides a flexible stand that includes a flexible arm constructed from a plurality of polymer segments that are selectively connected by a ball-and-socket system. The segments can be locked into position or held by friction alone. The stand 100 is shown in detail in FIG. 1. In one arrangement, it consists of an upright post 102 that rests on the ground that supports the proximal end 108 of the flexible arm 104. Note that the arm segments are covered by a sterile sheet 106. Alternatively, the flexible arm can be supported from a ceiling or wall mount, a cart or an imaging device housing, among other surfaces. The arm's distal end 110 carries a mounting bracket 112 that engages a medical ultrasound probe in this example. The probe is held firmly using clamps, friction, set screws or another mechanism. In use, the practitioner 116 manipulates the flexible arm, mounting and probe into an appropriate orientation against the patient 120, and then fine tunes the probe's position with respect to the target area on the patient to obtain the desired image, which is transmitted via a cable 130 to an imaging device (not shown). Either the inherent friction generated between arm segments or a positive locking mechanism holds the probe stationary against the target area, allowing the practitioner 116 to use both hands to administer appropriate treatment via needles and the like, while observing the path of the needle into the patient's body on the display.
The task of manipulating the probe into the optimum position for imaging the target involves moving the mounting/probe in several degrees of freedom. Referring to FIGS. 2-4, a prior art freehand, probe-manipulation technique is shown and described. In FIG. 2, the practitioner's hand 200 manipulates the probe 210 to establish an appropriate lateral alignment, using a side-to-side motion (arrows 220). This positions the probe at the appropriate point on the patient's body.
Once the general location has been established, the practitioner's hand 200 rotates (arrows 300) the probe 210 with respect to the target area so that it is oriented to properly face the region being imaged. The practitioner may consult the display of the imaging device to establish the proper rotational orientation. The display should provide an image that is, in essence, “right-side-up” with respect to the practitioner's point of view. Rotation will establish the appropriate orientation, and also produce the best image of the target area.
The next adjustment is tilt, which is shown in FIG. 4. In general, the practitioner's hand 200 must tilt (arrows 400) the probe 210 so that its face is generally orthogonal to the target surface. If the probe's face is skewed to the target surface, the image will be inferior or unreadable. This orientation, like alignment and rotation, is established based upon feedback from the viewed imager display.
The order of adjustments as described above can be varied and they can be carried out simultaneously.
The required adjustment of the probe in alignment, rotation and tilt can be labored using a relatively fixed holder on the above-described flexible arm. While the arm structure is technically capable of movement in each of the desired degrees of freedom, the segments tend to drag against each other frictionally when the arm is biased in a direction. This creates a situation where the practitioner tends to overshoot the desired target location. Thus, in practice, using the arm to manipulate each of alignment, rotation and tilt can prove laborious and inaccurate.
Thus, it is desirable to provide a more localized mechanism on a flexible arm, adjacent to a practitioner's hand, for manipulating the alignment, rotation and tilt of held probe. It is also desirable to provide a probe holder that effectively and firmly grasps a variety of probe sizes and form factors and that allows easy attachment and detachment of the probe from the holder.